1. Field of the Invention
This invention concerns lubricant additives and oil compositions containing and made with such additives. More particularly, this invention concerns mixtures of mono- or diesters of polyoxyalkylene diols with aminopolyazole which give increased oxidation and corrosion resistance to lubricants, like diesel engine oil.
2. Description of Related Information
Lubricants, while used primarily for lubrication, frequently need other properties, such as oxidation and corrosion resistance, to be used effectively. For example, lubricants used in the crankcases of large diesel engines, such as marine and railway diesel engines, are often subjected to operating conditions requiring special considerations. In particular, poor grade fuels, such as marine residual fuel, can be mixed with regular diesel fuel, such as D-2, for fuel cost savings. However, engine performance problems, such as increased corrosion and poor oxidative stability often arise. Additionally, new and more fuel efficient railway diesel engines place greater demands on the oxidation resistance of lubricants. Since oxidized lubricants cause increased engine corrosion, lubricants used for such newer engines are routinely changed more frequently to prevent such corrosive attack to avoid catastrophic engine failure.
Various additives have been used to improve the anti-oxidancy and corrosion resistance of lubricants. For example, calcium sulfurized alkyl phenolates have been effective. These compounds are typically made by processes including expensive recovery procedures and hazardous byproducts difficult to dispose of in an environmentally sound way. Alternatively, calcium sulfurized phenolates, made by a process using lime as the calcium source to avoid such processing problems, fail to provide a high level of oxidation and corrosion resistance.
Other oxidation and corrosion resistant additives have also been developed. For example, U.S. Pat. No. 4,464,276 (Sung et al.) discloses polyoxyalkylene polyamine triazole complexes as additives for lubricants having improved oxidative stability and corrosion control. U.S. Pat. No. 4,758,363 (Sung et al.) discloses the reaction product of esters of hydroxybenzoic acid and polyoxyalkylene polyol reacted with equimolar amounts of aldehyde or ketone and substituted or unsubstituted heterocyclic azole for improved oxidation and corrosion resistance of lubricating oils for diesel engines. U.S. Pat. No. 4,808,335 (Sung et al.) discloses reaction products of N-acyl sarcosine reacted with substituted or unsubstituted heterocyclic azole for improving oxidation and corrosion resistance of diesel engine lubricating oils.